\[\boxed{\text{423\ (423).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[y = x - 3\]
\[при\ \ x = 4 \Longrightarrow \ \ y = 1;\]
\[при\ \ x = 6 \Longrightarrow \ \ y = 3.\]